Rotary drilling machines



March 29, 1960 R. M. F. SEAWRIGHT 2,

, ROTARY DRILLING MACHINES Filed July 5, 1956 2 Sheets-Sheet 1 I71 verb-Rebel-i M- E Jezwriglz y W1 7 w March 29, 1960 I R. M. F. SEAWRIGHTROTARY DRILLING MACHINES 2 Sheets-Sheet 2 Filed July 5, 1956 QM, hm km 1b 1 E 7 \m h M N lfixmm In ve-nloh United States Patent 2,930,587 ROTARYDRILLING MACHINES Robert M. F. Seawright, Craighall Park,

Transvaal, Union of South Africa Application July 5, 1956, Serial No.595,918

Claims priority, application Union of South Africa July 7, 1955 Claims.(Cl. 255-47) This invention relates to rotary rock-drilling machinesdriven by motors utilizing pressure fluid and is a contin uation-in-partof my abandoned application Serial No. 477,680, filed on December 27,1954.

In machines of this kind in which the drilling tool is advanced underpower, it is customary to use a single motor for both rotation andadvance of the tool, the drives being transmitted through suitablegearing.

Since the optimum relationship between rotational speed and speed ofadvance is one that must of necessity vary considerably in practice, itis usual to provide means such as a gearbox to enable the relationshipto be varied at will. However, this expedient is far from satisfactorysince, even in the hands of an experienced operator sudden changes inthe penetrability of the rock being bored or progressive blunting of thecutting formations may cause the tool to be overor under-fed.

To avoid damage to the tool and the machine by overfeeding, it has beenproposed to interpose a slipping clutch in the feed mechanism. Thisdevice, however, introduces a wearing part which has to be periodicallyreplaced and is in any case no more than an energy-wasting palliative.

An object of the present invention is to provide a inachine in which therate of feed is automatically adjusted to suit the drilling condition.

A further object of the invention is to provide a drilling machine withtwo motors in which the behaviour of one motor is arranged to begoverned by and be dependent on the behaviour of the other.

Another object of the invention is to provide a rock drilling machine inwhich such behaviour of the one motor is governed with reference to thepower of the other motor or a parameter of the power of the other motor.t

The invention is described hereunder with reference to the accompanyingdrawings, in which Figure 1 isa diagrammatic view of one arrangement,

Figure 2 is a vertical section through a machine embo'dying thearrangement of Figure 1, t

Figure 3 is a side View of the embodiment of Figure 2,

Figure 4 is a vertical section through one oreach of the motors, whereit or they are constructed to allow variation of the power output.

In Figure 1 the machine comprises a splined feedscrew provided with achuck 11 for the drilling tool. Rotation is imparted to the feedscrew byaribbed collar 12 which engages the splines 13 and is gdrive'n through ageartrain 14 from the first air motor 15.

The exhaust of the motor is fed to the second motor 16 which, throughgearing 17, rotates a feed nut 18 that is engaged with thescrew-threading of the feedscrew It).

Means is comprised to feed a portion of the stream of pressure fluiddirectly to the second motor 16, the proportion of the stream fed to thetwo motors being ad justable by a control cock 19. The by-pass is fedinto the conduit 20 carrying the exhaust of the first motor 15, so thatthe by-passed pressure fluid supplements the back pressure at theexhaust of the first motor and Johannesburg,

amass? increases the admission pressure to the second motor 16,

and 3 a casing 30 encloses a part of the length of the feedscrew 10 andthe gearing whereby it is driven. The two air motors 15 and 16 arearranged in an extension 31 of the casing 30, in line with one another.The motors are of the eccentric rotor-sliding vane type and areconventional in operation.

The rotor shaft 32 of the motor 15 has mounted on it, outside the endwall 33, a pinion 34 which drives a gear wheel 35 that is bolted to acollar 12 that surrounds the feed shaft 10 and is engaged with itagainst relative rotag ,7 tion by keys 36 slidable in the splines 13 offeedscrew 10..

. The collar bearings 37.

The feed nut 18 is mounted for rotation in ball bearings 38 and isdriven by a gearwheel 41 secured to it, which in turn is driven by apinion 42. The pinion is carried by a cup-shaped extension 43 of theshaft 44 of the rotor of the second motor 16. The extension is supportedfor rotation on a ball bearing 45 the inner race of which is fitted ontothe end of the shaft 32 of the first motors rotor.

Pressure fluid is fed to the first motor 15 through a conduit 46 (Figure3). The exhaust fluid from the motor passes along a conduit 20 to theintake of the second motor 16. The second motor may receive all or partonly of the exhaust of the first motor, depending on the adjustment of athree way control cock 60, one way 48 of which is open to atmosphere.

Additionally, the second motor may receive part of the pressure fluidflowing in the conduit 46, the extent of the by-pass being controlled bythe cock 47; for the purpose discussed above in connection with Figure1.

The modified construction of Figure 4 is intended as an alternativearrangement tothat illustrated in Figures 1 and 2, in that variation ofthe power outputs of the two motors, achieved in Figures 1 and 2 byadjustment of the cocks 47 and 19, is effected in Figure 4 by manualvariation of the expansion ratios of one or both of the motors.

In Figure 4 the motor or each motor has a rotatable liner 50 having aninlet port 51 and two exhaust ports 52. The inlet port 51 registers withan arcuate chamber 53 defined between the liner and the casing 54 of themotor, which chamber receives pressure fluid through a conduit 55.

The liner is rotatable by means of a handle 56, the shank 57 of whichmoves within a slot (not shown) in the casing 54 and is screwed into ahole in the liner 50.

Movement of the handle 56 enables the inlet port 51 to be adjustedradially, to vary the expansion ratio of the motor; and also to reversethe motor by shifting the port to the other side of the contact zone ofthe liner and the rotor 58 of the motor.

The control means, whether it be the cocks 19 and 47 of the embodimentof Figures 1 and 2, or the handle 56 of Figure 4, allows the operator tocontrol the motors with nicety. The ratio of the power outputs of themotors can be adjusted to meet widely varying drilling conditions, or,by having the second motor underrun the first to withdraw the tool fromthe hole.

While in the procedures discussed it is the rotational motor, thebehaviour of which governs the behaviour of the feed motor, it will berealized that the reverse procedure may well be adopted.

In operation, when resistance to rotation of the tool increases, thefirst motor slows down, thereby decreasing the flow of pressure fluidthrough it. This in turn de- 12 is journalled inthe casing 30 in ballreducing the rate of" feed. The reduced rate 1 offeed reduces theresistance to the rotation of the tool which permits the first motor tospeed up thus increasing the rate of feed.

Thus the machine adapts 'itselfto'the drilling conditions it encountersas well as to the condition of the cutting formations. As thesedeteriorateythe machine automatically adjusts its rate of feed.

,It follows that'damage to the bit orcrown by*overfeeding is obviated,especially where the ground being drilled-is of varying character.

I claim:

'1. A rotary rock drilling-machine comprising a' drilling tool, feedmechanism for thetool, a motordrivenby pressure fluid vand arranged torotate=the-tool and a second fluid-operated motor arranged to 'berotatedby a portion ofthe pressure fluid supplemented by the residualenergy in the fluid exhausted-from the first motor and arranged to drivethe feed mechanism.

2. The machine of claim 1 including valvermeans be I .4 tween the motorscontrollable to vary the portion of exhaust fluid-fromthe-firstmotor'whieh is fed to the second motor.

3. The machine of claim *1 including means adjustably 6 to vary theratio of the power outputs of the two motors.

4. The machine of claim 3, in which the means to vary the output ratioconsists in a by-pass between the inlet to the first-motor and the inletto the second motor and valve means operable to control flow ofpressurev fluid 10 along the bypass.

5. The machine of claim 3 in which the means to vary the output ratioconsists in means to vary the ex- 1} pansion ratio. of a motor.

15 References Cited in the file of this patent UNITED STATES PATENTS

